1. Field of the Invention
The present invention relates to a dial-display measuring tool using a dial-type display.
2. Description of Related Art
Various measuring tools use a dial display to output measurement results of the measuring tools. A wide variety of measuring tools of dial-display are available for different measurement purposes and different workpieces. A dial gauge, which is one of such tools, is a dimension measuring tool to read a dimension of a workpiece based on a rotation amount of its pointer. The dial gauge is widely used as it may be attached to a measurement stand or installed into a jig or a testing tool, and it has a large variety to serve different applications. Particularly, a one-revolution dial gauge is useful for comparative measurements since users rarely make a mistake in reading the rotation amount of the pointer.
An example of a conventional one-revolution dial gauge is illustrated in Japanese Laid-open utility model publication No. Sho 62-34241 and FIGS. 8 to 10.
FIG. 8 is an exploded perspective view showing the example of the conventional one-revolution dial gauge. In FIG. 8, the one-revolution dial gauge 100 includes a gauge body 10, a dial face 130 provided on a base plate 12 of the gauge body 10 with a leaf spring 7 interposed therebetween, a pointer 5 attached to the centre of the gauge body 10, and a bezel 160 covering the dial face 130 and the pointer 5.The gauge body 10 includes a cylindrical casing and axially slidably supports a spindle 2 passing through the gauge body 10, the spindle 2 having a contact point 21 at an end thereof. The spindle 2 and the contact point 21 constitute a probe. The pointer 5, which is arranged at the center of the base plate 12 of the gauge body 10, rotates in response to a movement of the contact point 21 of the spindle 2. The bezel 160 is attached to the gauge body 10 to cover the dial face 130 and the pointer 5.
FIG. 9 is an enlarged view showing the dial face 130 in the conventional art. In FIG. 9, the dial face 130 has graduations 133 arranged at regular circumferential intervals and a dead zone 134 indicating an area where measurement accuracy is not assured. Further, the dial face 130 has a notch 131 while the bezel 160 has a projection 162 at a position matching the notch 131. The projection 162 is fitted into the notch 131 so that the dial face 130 is fixed to the bezel 160 not to be rotated separately.
The leaf spring 7 biases the dial face 130 toward the bezel 160 for avoiding errors in reading measurements due to a misalignment of the dial face 130.
A pointer attachment process, which is a process to attach the pointer 5 onto a pointer shaft 11, included in a production process of the one-revolution dial gauge 100 is descried with reference to FIG. 10. In the conventional one-revolution dial gauge 100, the leaf spring 7 interposed between the dial face 130 and the base plate 12 keeps the dial face 130 shaky and unstable. Because of this, in positioning the dial face 130, a temporary bezel 8 without a cover plate is set on the gauge body 10. Then a projection 81, which is formed in advance in the temporary bezel 8, is fitted into the notch 131 of the dial face 130 to fix the dial face 130, and thereafter the pointer 5 is attached. Once the pointer 5 is attached, the temporary bezel 8 is removed and the bezel 160 is set thereon.
In use of such one-revolution dial gauge 100 of the conventional art, users occasionally rotate the dial face 130 to change the measurement orientation. If the bezel 160 is rotated, the dead zone 134, which is integrally formed on the dial face 130, is rotated together with the dial face 130. In this situation, when the pointer 5 points within the area of non-assured measurement accuracy but not indicated by the dead zone 134, the users might read an incorrect graduation. Also, an area of assured measurement accuracy might be indicated by the dead zone 134. To avoid human errors due to these, some solution is required.
Further, since the dead zone 134 is integrally formed with the dial face 130, the dial face 130 is used only for the one-revolution dial gauge and cannot be alternated with dial faces of other standard dial gauges, thus becoming an obstacle to component sharing.